Broadband acoustic observations of individual naturally occurring hydrate-coated bubbles in the Gulf of Mexico Free

Methane has been observed escaping from the seafloor as free gas bubbles. During ascent through the watercolumn, these bubbles undergo several processes, including accumulation of surfactants on the bubble surface. Surfactants have been theorized to increase the longevity of bubbles, facilitating methane transport to the upper ocean. Surfactants take many forms, including biological detritus, oil coatings, and hydrate shells. In 2011 and 2012, hydrate shelled bubbles were visually observed by ROV Hercules in the Northern Gulf of Mexico at the Biloxi Dome. The NOAA Ship Okeanos Explorer returned to the Biloxi Dome in March of 2018 with a broadband (10 kHz bandwidth) echosounder with vertical range resolution of approximately 7 cm. Individual bubbles were acoustically observed, rising from the seafloor several hundred meters before exiting the echosounder beam. In addition, the Okeanos Explorer made multiple survey passes over the seep site, mapping the vertical rise of the bubble plume at almost 1000 m. The dataset supports detailed modeling of the effects of hydrate coatings on acoustic response and provides an opportunity to estimate the dissolution rate of naturally occurring hydrate-coated bubbles.